Adjusting Cardiac Pacing Response Sensing Intervals
Discrimination between different types of possible cardiac pacing responses may depend on the timing of expected features that are sensed within a temporal framework. The temporal framework may include classification intervals, blanking periods and appropriately timed back up paces. The classification intervals and blanking periods of the temporal framework are intervals of time that have time parameters that include start time, end time, and length. The relationships and timing parameters of the elements of the temporal framework, e.g., blanking periods, classification intervals, delay periods, and backup pacing, should support detection of features used to discriminate between different types of pacing responses. As the system learns the morphology of the particular patient by analyzing the waveform of the pacing response signal, the temporal framework for pacing response determination may be adjusted to accommodate the individual patient.
This application claims the benefit of Provisional Patent Application Ser. No. 61/419,140, filed on Dec. 2, 2010, to which priority is claimed pursuant to 35 U.S.C. §119(e) and which is hereby incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates generally to implantable medical devices and, more particularly, to cardiac pacing response classification.
BACKGROUNDCardiac pacing devices operate to stimulate the heart tissue electrically coupled to the electrodes to produce a contraction of the tissue. Pacemakers deliver a series of low energy pace pulses timed to assist the heart in producing a contractile rhythm that maintains cardiac pumping efficiency. Pace pulses may be intermittent or continuous, depending on the needs of the patient. There exist a number of categories of cardiac devices that provide pacing pulses, with various modes for sensing and pacing one or more heart chambers.
When a pace pulse produces a contraction in the heart tissue, the electrical cardiac signal following the contraction is denoted the evoked response signal. A pace pulse must exceed a minimum energy value, or capture threshold, to produce a contraction. It is desirable for a pace pulse to have sufficient energy to stimulate capture of the heart without expending energy significantly in excess of the capture threshold. Thus, accurate determination of the capture threshold may be required for efficient pace energy management. If the pace pulse energy is too low, the pace pulses may not reliably produce a contractile response in the heart and may result in ineffective pacing. If the pace pulse energy is too high, the patient may experience discomfort and/or the battery life of the device will be shorter.
Capture detection allows the cardiac device to adjust the energy level of pace pulses to correspond to the optimum energy expenditure that reliably produces a contraction. Further, capture detection allows the cardiac device to initiate a back-up pulse whenever a pace pulse does not produce a contraction.
SUMMARYEmbodiments described herein involve methods of operating a cardiac device. Pacing pulses are delivered to a heart chamber during a cardiac cycle. A cardiac pacing response signal of the heart chamber is sensed during the cardiac cycle and following the pacing pulse in one or both of a first classification interval and a second classification interval, each of the first and second classification intervals associated with one or more timing parameters including at least a start time. At least one timing parameter of the first classification interval, the second classification interval, and one or more blanking periods is adapted based on timing of at least one signal feature of the pacing response signal and a temporal relationship between the first classification interval and the second classification interval. In some embodiments the signal feature comprises a positive or negative peak. The first and second classification intervals, having the adapted timing parameters to a subsequent pacing response signal sensed following a subsequent pacing pulse delivered to the heart chamber, are applied. It is determined whether the signal feature of the subsequent pacing response signal falls within the first or second classification intervals that have the same timing parameters. A pacing response of the heart chamber to the to the subsequent cardiac pacing pulse based on a determination that the signal feature falls within the first or second classification intervals having the adapted timing parameters is classified. Cardiac therapy is delivered based on the classification of the pacing response.
In some implementations adapting the timing parameters based on the temporal relationship of the first and second classification intervals comprises adapting a start time of the second classification interval based on an end time of the first classification interval. In other implementations adapting the timing parameter comprises adapting a timing parameter of a blanking period based on a temporal relationship between the blanking period and one or both of the first classification interval and the second classification interval. In yet another implementation adapting the timing parameter comprises adapting timing parameters of three classification intervals, the first classification interval used to detect possible capture or fusion, the second classification interval used to confirm fusion, and a third classification interval used to confirm capture. In some embodiments adapting the timing parameter comprises at least one of shortening one or more of the blanking periods and lengthening one or more of the first and second classification intervals and lengthening one or more of the blanking periods and shortening one or more of the first and second classification intervals.
According to some embodiments an amount of change in the timing of the signal feature is compared to an initial timing of the signal feature to a threshold and a determination is made whether to adapt one or both of the first and second classification intervals based on the comparison of the amount of change. Some implementations may also include comparing an amount of change in the timing of the signal feature compared to an initial timing of the signal feature to a threshold and determining whether to re-initialize timing parameters of the first classification interval, the second classification interval, and the one or more blanking periods, wherein re-initializing the timing parameters involves acquiring a multi-sample electrogram of a pacing response signal.
Embodiments described herein include a device comprising pacing circuitry configured to deliver a pacing pulse to a heart chamber during a cardiac cycle. The device also includes sensing circuitry configured to sense a cardiac pacing response signal of the heart chamber during the cardiac cycle and following the pacing pulse in one or both of a first classification interval and a second classification interval, each of the first and second classification intervals associated with one or more timing parameters including at least a start time. Additionally, the device includes control circuitry configured to adapt at least one timing parameter of one or more of the first classification interval, the second classification interval, and one or more blanking periods based on timing of at least one signal feature of the pacing response signal and a temporal relationship between the first classification interval and the second classification interval. The control circuitry is also configured to apply the first and second classification intervals having the adapted timing parameters to a subsequent pacing response signal sensed following a subsequent pacing pulse delivered to the heart chamber and to determine if the signal feature of the subsequent pacing response signal falls within the first or second classification intervals that have the adapted timing parameters. The control circuitry may also be configured to classify a pacing response of the heart chamber to the subsequent cardiac pacing pulse based on a determination that the signal feature falls within the first or second classification intervals having the adapted timing parameters and to deliver cardiac therapy based on classification of the pacing response.
Some embodiments may include that the control circuitry is further configured to adapt the timing parameters based on the temporal relationship of the first and second classification intervals comprises adapting a start time of the second classification interval based on an end time of the first classification interval. In some implementations that control circuitry may also be configured to adapt a timing parameter of a blanking period based on a temporal relationship between the blanking period and one or both of the first classification interval and the second classification interval. Additionally, in some embodiments, the control circuitry my be further configured to adapt timing parameters of three classification intervals, the first classification interval used to detect possible capture or fusion, the second classification interval used to confirm fusion, and a third classification interval used to confirm capture. Some implementations may also include that the control circuitry is further configured to compare an amount of change in the timing of the signal feature compared to an initial timing of the signal feature to a threshold and to determine whether to adapt one or both of the first and second classification intervals based on the comparison of the amount of change.
Some embodiments for operating a cardiac device include delivering at least one pacing pulse to a heart chamber and sensing a pacing response signal of the heart chamber following the pacing pulse. The embodiments may also include detecting a temporal event of the pacing response signal, the temporal event comprising a point in time that falls between a first feature and a second feature of the pacing response signal. Additionally, in some embodiments of operating a cardiac device include initializing timing parameters of one or more of pacing response classification intervals and one or more blanking periods based on the detected temporal event so that the first feature falls within a first classification interval and the second feature falls within a second classification interval.
Some implementations may include that sensing the pacing response further comprises acquiring a multi-sample of the pacing response signal. In other embodiments may include that wherein detecting the temporal event comprises detecting a zero crossing point of the pacing response signal. In other implementations detecting the temporal event comprises detecting an inflection point of the pacing response signal. In yet other implementations detecting the temporal event comprises detecting a midpoint between a time of occurrence of the first feature and a time of occurrence of the second feature. Some embodiments further include detecting the temporal event comprises detecting a zero crossing point or an inflection point of the cardiac signal initializing the timing parameters of the one or more classification intervals and the one or more blanking periods comprises setting a start time of a blanking period and an end time of a classification interval to coincide with the zero crossing point or inflection point. Some embodiments may further include initializing the timing parameters of the one or more blanking periods to allow sensing of the first or second feature and/or initializing the timing parameters of the one or more blanking periods to prevent sensing of signal features other than the first or second features
Embodiments described herein include a cardiac device comprising pacing circuitry configured to deliver at least one pacing pulse to a heart chamber. In this case, the cardiac device also includes sensing circuitry configured to sense a pacing response signal of the heart chamber following the pacing pulse and detect a temporal event of the pacing response signal, the temporal event comprising a point in time that falls between a first feature and a second feature of the pacing response signal. The cardiac device may also include control circuitry configured to initialize timing parameters of one or more of pacing response classification intervals and one or more blanking periods based on the detected temporal event so that the first feature falls within a first classification interval and the second feature falls within a second classification interval.
Some implementations described herein include that the sensing circuitry is further configured to acquire a multi-sample electrogram of the response signal. Additional embodiments include that the sensing circuitry is further configured to detect a zero crossing point or an inflection point of the cardiac signal and that the control circuitry is further configured to initialize the timing parameters of the one or more classification intervals and the one or more blanking periods and to set a start time of a blanking period and an end time of a classification interval to coincide with the zero crossing point or inflection point.
For some implementation a method includes delivering a pacing pulse to a left ventricle of a heart and sensing a cardiac pacing response signal of the left ventricle. The method also includes detecting a first peak in a first capture detection interval and detecting a second peak in one of a fusion detection interval and a second capture detection interval that follows the fusion detection interval. Additionally the method comprises discriminating between capture and fusion based on the first and second peaks.
In some implementations detecting the first peak in the first capture detection interval comprises detecting the first peak in a capture detection region within the first capture detection interval, the capture detection region having upper and lower timing boundaries and upper and lower amplitude boundaries. In other implementations, discriminating between capture and fusion comprises classifying the pacing response as potential capture if the first peak falls within the capture detection region and confirming capture if the second peak falls within the second capture detection interval. In additional embodiments discriminating between capture and fusion comprises classifying the pacing response as fusion if the first peak falls does not within the capture detection region or confirming fusion if the second peak falls within the fusion detection interval.
Implementations described herein include a device comprising pacing circuitry configured to deliver a pacing pulse to a left ventricle of a heart. The device also includes sensing circuitry configured to sense a cardiac pacing response signal of the left ventricle and detect a first peak in a first capture detection interval and detecting a second peak in one of a fusion detection interval and a second capture detection interval that follows the fusion detection interval. Additionally, the device includes control circuitry configured to discriminate between capture and fusion based on the first and second peaks. In some implementations the sensing circuitry is configured to detect the first peak in a capture detection region within the first capture detection interval, the capture detection region having upper and lower timing boundaries and upper and lower amplitude boundaries.
The above summary is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims in conjunction with the accompanying drawings.
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail below. It is to be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
DESCRIPTION OF VARIOUS EMBODIMENTSIn the following description of the illustrated embodiments, references are made to the accompanying drawings forming a part hereof, and in which are shown, by way of illustration, various embodiments by which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural and functional changes may be made without departing from the scope of the present invention.
Systems, devices or methods disclosed herein may include one or more of the features, structures, methods, or combinations thereof described herein. For example, a device or system may be implemented to include one or more of the advantageous features and/or processes described below. It is intended that such device or system need not include all of the features described herein, but may be implemented to include selected features that provide for useful structures and/or functionality. Such a device or system may be implemented to provide a variety of therapeutic or diagnostic functions.
After delivery of a pacing pulse to a heart chamber, various cardiac responses to the pacing pulse are possible. In one scenario, the pacing pulse may generate a propagating wavefront of depolarization resulting in a contraction of the heart chamber. In this scenario, the pacing pulse is said to have captured the heart chamber. Capture of the heart chamber may occur if the pacing pulse has sufficient energy and is delivered during a non-refractory period. If the pacing pulse does not produce contraction of the chamber, the cardiac response is referred to as non-captured beat. Non-capture may occur, for example, if the pacing pulse energy is too low, and/or if the pacing pulse is delivered during a refractory period of the cardiac tissue. Fusion occurs when a depolarization initiated by a pace merges with an intrinsic depolarization.
The cardiac pacing response may be determined using a variety of approaches. For example, the cardiac signal sensed following a pacing pulse may be evaluated to discriminate between various pacing responses, e.g., noncapture, capture, fusion, and noncapture with intrinsic activation. Cardiac pacing response classification depends on consistent signal morphology of cardiac signals following the pacing pulse. In some implementations, where feature timing is relatively consistent, the expected timing of the features used for cardiac response determination may be established by the system based on the previous cardiac cycles. For a particular patient, the system may “learn” to expect certain features to occur around a particular time after delivery of the pacing pulse based on the historical timing of the features over a number of previous cardiac cycles.
Discrimination between different types of possible cardiac pacing responses may depend on the timing of expected features that are sensed within a temporal framework. The temporal framework may include classification intervals, blanking periods and appropriately timed back up paces. The classification intervals and blanking periods of the temporal framework are intervals of time that have time parameters that include start time, end time, and length. The relationships and timing parameters of the elements of the temporal framework, e.g., blanking periods, classification intervals, delay periods, and backup pacing, should support detection of features used to discriminate between different types of pacing responses. As the system learns the morphology of the particular patient by analyzing the waveform of the pacing response signal, the temporal framework for pacing response determination may be adjusted to accommodate the individual patient.
The classification intervals 140, 150 define time periods in which features of the pacing response signal can be detected to classify the heart chamber's response following the pacing pulse 105. For example, the pacing response signal may indicate that the heart chamber's response following the pacing pulse 105 is non-capture, fusion, capture, or intrinsic. The features which indicate the pacing response may be one or a combination of positive peaks, negative peaks, slopes, inflection points, zero crossing, and/or other cardiac signal features. In some embodiments, if the cardiac signal sensed in the first classification interval 140 preliminarily indicates capture, the second classification interval 150 may be used to look for at least one feature to verify that capture has occurred. In some cases, more than two classification intervals may be used to classify the pacing response signal.
Each classification interval 140, 150 may be bounded in time and can be characterized by timing parameters including the start time of the classification interval, the length of the interval, and/or the end time of the interval. The timing parameters of the first interval 140 and the second interval 150, and/or the timing relationship between the first and second intervals 140, 150 may be established for cardiac response classification based on the timing of one or more pacing response signal features within at least one of the classification intervals 140, 150. The timing relationship between the elements of the temporal framework may or may not involve a cause and effect relationship. For example, each of classification intervals, delay periods, blanking periods, and back up pacing may be considered temporal framework elements. If the timing of one of these elements is modified, this timing change may necessitate a timing change in the timing of one or more other element.
In some cases, delaying the start time of the first interval 140 may also have the effect of delaying the start time of the second interval 150. Alternatively, the length of the first interval 140 could be shortened as well as the start time delayed and the second interval 150 may remain unchanged. The two intervals 140, 150 could also overlap in time allowing the second interval 150 to start at its original starting time even if the first interval 140 is delayed or lengthened. Timing parameters of the second interval 150 may also be changed and may have an effect on the timing parameters of the first interval 140. According to some embodiments, the timing parameters of the first interval 140 and the timing parameters of the second interval 150 are determined independently of one another.
In the embodiment illustrated in
The first blanking period 205 may be implemented on sense channels that sense in the same chamber as the pacing pulse 105. Blanking periods may additionally or alternatively be implemented on sense channels that sense in one or more other heart chambers, e.g., the contralateral heart chamber and/or the ipsilateral heart chamber to the chamber being paced. As shown in
Because sensing is disabled during blanking, a blanking period that is too long may prevent features of the pacing response signal from being detected. In these cases, the length of the blanking period may need to be modified to avoid undersensing of signal features.
In
The approaches described herein are particularly useful for capture threshold testing and may also be used during therapeutic pacing (non capture threshold testing) with capture verification. During a capture threshold test and/or automatic capture verification, back up paces may be delivered to ensure continued pacing support in the event of persistent non-capture. In some cases, back-up pacing is applied only if noncapture is detected after an initial pace. In some capture threshold test implementations, a back-up pace is delivered after every test pace of the capture threshold test.
The implementation shown in
In some approaches, the timing of the back-up pace 242 and the timing parameters of the second blanking period 244 may be determined based on the timing of one or more cardiac signal features indicative of the cardiac pacing response. For example, the back-up pace 242 may be delivered before cardiac signal features indicative of capture, fusion or a non-captured/intrinsic response are expected to occur. The length and/or the start time of the second blanking period 244 that follows the back-up pace 242 may be adjusted to facilitate sensing of the cardiac features used for pacing response classification.
A second classification interval 150 follows the second blanking period 244 in
As described in connection with
Each classification interval 140, 150 and blanking period 205, 244 can be characterized by timing parameters including the start time of the interval or period, the length of the interval or period, and/or the end time of the interval or period. The back-up pace 242 is also characterized by the time of the back-up pace event 242. The temporal framework, including the timing parameters of the classification intervals 140, 150, blanking periods 205, 244, and back-up pace 242, as it is imposed on a pacing response signal, can determine the effectiveness of the pacing response classification. For example, if a blanking period is too long, features of interest may not be detected. In another example, a classification interval may be too short, missing important response signal features.
The classification intervals 140, 150, the blanking periods 205, 244, and the back-up pace 242 are events that can be temporally related. The temporal relationships between these events affect successful pacing response classification. Changing a timing parameter of one event may cause a change in the timing of other events. For example, delaying the start time of the first classification interval 140 may also have the effect of delaying the time of the back-up pace 242. Delaying the back-up pace may also delay the start time of the second blanking period 244, and/or the second classification interval 150. As another example, if the first classification interval is shortened, the timing parameters of the first blanking period 205 may remain unchanged or the first blanking period 205 may also be shortened. Shortening the first classification interval 140 may move the start time of the back-up pacing pulse 242. According to some embodiments, the timing parameters of two or more of the first classification interval 140, the second classification interval 150, the first blanking period 205, the second blanking period 244, and the back-up pace 242 are not temporally related and may be determined independently of one another.
In
Adaptation of the temporal framework elements may enhance pacing response classification.
The elements of the temporal framework used in pacing response classification may be adjusted so that features of interest fall appropriately within the classification intervals and are not blanked by the blanking periods. For example, adjustment of the intervals and/or blanking periods and/or other elements can be based on the feature timing for a particular type of pacing response to achieve optimal feature detection. In some cases, pacing response classification is achieved based on one or multiple features of the pacing response signal. The use of cardiac response features for response classification is further described in commonly owned U.S. Pat. Nos. 7,319,900, 7,774,064, 7,337,000, 7,499,751, and 7,574,260, which are incorporated herein in their respective entireties.
Initialization of the classification intervals may occur prior to or during use of the temporal framework to determine the cardiac pacing response. For example, the initialization may be performed fully automatically by the cardiac pacing device, or may be performed partially automatically by a physician operating a device programmer to program the pacing device with appropriately timed intervals/periods. For example, a pacing device and/or device programmer may suggest or indicate appropriate timing parameters for the classification intervals/delay periods that can be accepted by a physician to be programmed into the cardiac pacing device.
Timing parameters of one or more of a first classification interval and a second interval are then initialized 540 based on the temporal event. For example, in some cases, the timing parameters of the classification intervals/delay periods may be initialized so that a first feature of the pacing response signal falls within the first classification interval and the second feature falls within the second classification interval. In some cases, an end and/or start time of a classification interval and/or blanking period may be initialized based on a zero crossing point, an inflection point, or some other temporal event of the pacing response signal. In yet other cases, the timing parameters of classification interval and/or blanking period are calculated based on a temporal distance between a feature of the cardiac response signal and the start and/or end time of the classification interval and/or blanking period. After initialization, the parameters are stored for future use in capture verification during therapeutic pacing and/or for use in capture threshold testing.
In some cases, the timing of the temporal event may be used to establish the timing of a back up pace and a corresponding blanking period, as illustrated in
In some implementations, the temporal event used to determine the timing of the back up pace, classification intervals and/or blanking periods is a point in time between the time coordinates of two cardiac signal features, which may or may not be the same features used to classify the pacing response. In
In some cases, multiple temporal events may be used in establishing the backup pace timing and/or parameters of the classification intervals and/or blanking periods. For example, in the implementation illustrated in
Initialization and the adjustment of timing parameters of elements of the temporal framework may help to achieve more accurate pacing response classification.
After initialization, acute and/or chronic changes in patient physiology, disease conditions, device parameters, and/or other factors may cause a shift in the timing of signal features used for pacing response classification. The initial timing parameters for pacing response classification may be adapted from time to time to accommodate these changes. In some cases, an initialization may be performed before each capture threshold test to establish the temporal framework for pacing response classification. In some cases, after a first initialization, the process may include checking to determine if the timings of the features of interest have shifted, and if so the timing parameters of the temporal framework may be adjusted to accommodate the feature timing shifts. The adjustments may or may not require capture of a multi-sample EGM signal and could be based on a few selected features of the cardiac signal rather than the EGM. In some implementations, the current timing of signal features may be compared to the initial timing parameters to determine if a shift in the timing of the signal features has occurred. If a shift in the timing of signal features has occurred, the process may involve adjusting the temporal framework based on the timing shift. Alternatively, the system may re-initialize the temporal framework by acquiring and using an EGM signal. The determination to re-initialize the temporal framework may be based on an offset period between the initial feature timings and the current feature timings being larger than a preset threshold. In some cases, re-initialization of the temporal framework only occurs when persistent loss of capture or fusion is detected.
Turning now to
To illustrate,
Cardiac pacing response classification may be implemented during capture threshold testing and/or non-capture threshold test therapeutic pacing for biventricular pacing. Biventricular pacing has been shown to improve the outcomes for people who suffer from congestive heart failure. Effective biventricular pacing depends on consistent capture by pacing pulses applied to both the right and left ventricles.
If the peak of the pacing response signal exceeds the threshold 1340 and is detected within a capture detection region 1315 in the first capture detection interval 1310, then the pacing response is determined to be potential capture and capture is confirmed based on the pacing response signal sensed during the second and third classification intervals 1320, 1330. In some cases, the peak of a fusion response signal may be detected in the capture detection region 1315 and, in these cases, the pacing response signal in the second and third classification intervals 1320, 1330 is used to discriminate between capture and fusion.
In the illustrated example, the second classification interval 1320 is used to confirm or detect fusion and is denoted herein as the fusion detection interval. In this example, the fusion detection interval 1320 starts at about 70 milliseconds after the pacing pulse and continues for about 40 milliseconds. The fusion detection interval 1320 may start earlier or later and may be a longer or shorter period of time than is depicted in
In some implementations a capture detection region 1315 is used within the first capture detection interval 1310. The capture detection region 1315 has upper and lower time boundaries and upper and lower amplitude boundaries. If the first peak of the pacing response signal falls within the capture detection region 1315, capture is indicated but may not confirmed until the second peak of the pacing response signal is detected in the second capture detection region 1330. Confirmation of potential fusion or potential capture using the fusion detection interval 1320 and the second capture detection interval 1330 is useful because of the similar left ventricular signal morphologies for fusion and capture, which can cause the first signal peaks for these responses to have similar timings and/or amplitudes.
Referring now to
The lead system 1602 is used to detect electric cardiac signals produced by the heart and to provide electrical energy to the heart under certain predetermined conditions to treat cardiac arrhythmias. The lead system 1602 may include one or more electrodes used for pacing, sensing, and/or cardioversion/defibrillation. In the embodiment shown in
The lead system 1602 may include intracardiac leads implanted in a human body with portions of the intracardiac leads inserted into a heart. The intracardiac leads include various electrodes positionable within the heart for sensing electrical activity of the heart and for delivering electrical stimulation energy to the heart, for example, pacing pulses and/or defibrillation shocks to treat various arrhythmias of the heart.
The lead system may include one or more extracardiac leads having electrodes, e.g., epicardial electrodes, positioned at locations outside the heart for sensing and pacing one or more heart chambers.
The right ventricular lead system illustrated in
In one configuration, the RV-tip electrode 1653 referenced to the can electrode 1681b may be used to implement unipolar pacing and/or sensing in the right ventricle. Bipolar pacing and/or sensing in the right ventricle may be implemented using the RV-tip and RV-ring electrodes 1653, 1663. In yet another configuration, the RV-ring 1663 electrode may optionally be omitted, and bipolar pacing and/or sensing may be accomplished using the RV-tip electrode 1653 and the RV-coil 1642, for example. The right ventricular lead system may be configured as an integrated bipolar pace/shock lead. The RV-coil 1642 and the SVC-coil 1641 can be used as defibrillation electrodes.
The left heart lead includes an LV distal electrode 1655 and an LV proximal electrode 1654 located at appropriate locations in or about the left ventricle for sensing signals of the left ventricle and/or delivering electrical stimulation to left ventricle. In the example of
Unipolar pacing and/or sensing in the left ventricle may be implemented, for example, using the LV distal electrode 1655 referenced to the can electrode 1681b. The LV distal electrode 1655 and the LV proximal electrode 1654 may be used together as bipolar sense and/or pace electrodes for the left ventricle. The electrode vector used for cardiac response classification may include, for example, any unipolar, extended bipolar and/or bipolar combination. The electrode vector used for cardiac response classification can be determined for a particular pacing vector. The left heart lead and the right heart leads, in conjunction with the ICD 1600, may be used to provide cardiac resynchronization therapy such that the ventricles and/or atria of the heart are paced substantially simultaneously, or in phased sequence, to provide enhanced cardiac pumping efficiency for patients suffering from congestive heart failure.
The right atrial lead includes a RA-tip electrode 1652 and an RA-ring electrode 1651 positioned at appropriate locations in the right atrium for sensing and pacing the right atrium. In one configuration, the RA-tip 1652 referenced to the can electrode 1681b, for example, may be used to provide unipolar pacing and/or sensing in the right atrium. In another configuration, the RA-tip electrode 1652 and the RA-ring electrode 1651 may be used to effect bipolar pacing and/or sensing.
Referring now to
The ICD 1600 depicted in
The ICD 1600 may be a programmable microprocessor-based system, including a control system 1720 and memory 1770. The memory 1770 may store programming instructions and/or parameters to achieve various pacing, defibrillation, and/or sensing functions. Further, the memory 1770 may store data indicative of cardiac signals received by other components of the ICD 1600. The memory 1770 may be used, for example, for storing EGM and historical therapy data. The data storage may include, for example, data obtained from long term patient monitoring used for trending or other diagnostic purposes. Historical data, as well as other information, may be transmitted to an external programmer unit 1790 as needed or desired.
The control system 1720 and memory 1770 may cooperate with other components of the ICD 1600 to control the operations of the ICD 1600. The control system 1720 depicted in
Telemetry circuitry 1760 may be implemented to provide communications between the ICD 1600 and an external programmer unit 1790. In one embodiment, the telemetry circuitry 1760 and the programmer unit 1790 communicate using a wire loop antenna and a radio frequency telemetric link, as is known in the art, to receive and transmit signals and data between the programmer unit 1790 and the telemetry circuitry 1760. In this manner, programming commands and other information may be transferred to the control system 1720 of the ICD 1600 from the programmer unit 1790 during and/or after implant. In addition, stored cardiac data pertaining to timing parameters of elements within a temporal framework for pacing response classification, for example, along with other pacing response classification data, may be transferred between the programmer unit 1790 and the ICD 1600.
In the embodiment illustrated in
A right atrial sensing circuit 1731 serves to detect and amplify electrical signals from the right atrium. A right ventricular sensing circuit 1732 serves to detect and amplify electrical signals from the right ventricle of the heart. A left atrial sensing circuit 1735 serves to detect and amplify electrical signals from the left atrium of the heart. A left ventricular sensing circuit 1736 serves to detect and amplify electrical signals from the left ventricle of the heart. The outputs of the switching matrix 1710 may be operated to couple selected combinations of electrodes 1651, 1652, 1656, 1657, 1654, 1655, 1641, 1642, 1663, 1653 to an evoked response sensing circuit 1737. The evoked response sensing circuit 1737 may serve to sense and amplify voltages developed using various combinations of electrodes for cardiac response classification. The outputs of the sensing circuits 1731-1737 are coupled to the control system 1720.
In the embodiments described herein, various combinations of pacing and sensing electrodes may be utilized in connection with pacing and sensing the cardiac signal following the pace pulse to classify the cardiac response to the pacing pulse. For example, in some embodiments, a first electrode combination is used for pacing a heart chamber and a second electrode combination is used to sense the cardiac signal following pacing. In other embodiments, the same electrode combination is used for pacing and sensing.
Sensing the cardiac signal following a pacing pulse using the same electrode combination for both pacing and sensing may yield a sensed cardiac signal including a pacing artifact component associated with residual post pace polarization at the electrode-tissue interface. The pacing artifact component may be superimposed on a smaller signal indicative of the cardiac response to the pacing pulse, i.e., the evoked response. The pacing output circuitry may include a coupling capacitor to block DC components from the heart and to condition the pacing stimulus pulse. The presence of a large pacing artifact signal may complicate the classification of the cardiac response to pacing. In some cases, the ICD may include circuitry to cancel the pacing artifact from the detected signal. Classification of the cardiac response to pacing may be implemented using the pacing artifact cancelled signal. Cancellation of the pacing artifact in cardiac response classification is particularly important when the same or similar electrode combinations are used both for delivering pacing pulses and for sensing the cardiac signals following the delivery of the pacing pulses.
In various embodiments described herein a first electrode combination may be used for pacing the heart chamber and a second electrode combination used for sensing the cardiac signals following the pace for cardiac response classification. If different electrode combinations are used for pacing and sensing, a temporal separation between the cardiac response signal, e.g., the captured response, and the pacing artifact may facilitate classification of the cardiac response to pacing without cancellation of the pacing artifact or with reduced circuitry for canceling the pacing artifact. The temporal separation occurs due to the propagation delay of the depolarization wavefront initiated at the pacing electrode and traveling to a sensing electrode that is physically spaced apart from the pacing electrode. The temporal separation of the cardiac response signal and the pacing artifact may be sufficient to make cancellation of the pacing artifact unnecessary.
The pacemaker control circuit 1722, in combination with pacing circuitry for the left atrium, right atrium, left ventricle, and right ventricle 1742, 1741, 1743, 1744, may be implemented to selectively generate and deliver pacing pulses to the heart using various electrode combinations. The pacing electrode combinations may be used to effect bipolar or unipolar pacing of the heart chambers as described above.
Possible sensing vectors for effecting cardiac response classification may include, for example, RV-tip 1653 and RV-coil 1642, RV-coil 1642 and LV distal electrode 1655, RV coil 1642 and LV proximal electrode 1654, RV-coil 1642 and can 1681b, RV-coil 1642 and SVC coil 1641, RV-coil 1642 and SVC coil 1641 tied and the can 1681b, RV-coil 1642 and RA-ring 1651, RV-coil 1642 and RA-tip 1652, LV distal electrode 1655 and LV proximal electrode 1654, LV distal electrode 1655 and can 1681b, LV distal electrode 1655 and SVC coil 1641, LV distal electrode 1655 and RA-ring 1651, LV distal electrode 1655 and RA-tip 1652, LV proximal electrode 1654 and can 1681b, LV proximal electrode 1654 and SVC coil 1641, LV proximal electrode 1654 and RA-ring 1651, LV proximal electrode 1654 and RA-tip 156, SVC coil 1641 and can 1681b, RA-ring 1651 and can 1681b, RA-tip 1652 and can 1681b, SVC coil 1641 and RA-ring 1651, SVC coil 1641 and RA-tip 1652, RA-ring 1651 and RA-tip 1652, RA-ring 1651 and can 1681b, RA-tip 1652 and RV-coil 1642, RA-ring 1651 and RV-coil 1642, RA-tip 1652 and RV-tip 1653, RA-ring 1651 and RV-tip 1653, RV-tip 1653 and can 1681b, RV-ring 1663 and can 1681b, LV distal electrode 1655 and RV-coil 1642, LV proximal electrode 1654 and RV-coil 1642, LV distal electrode 1655 and RV-ring 1663, and LV distal electrode 1655 and RV-ring 1663. Some embodiments may include vectors that use one or more left atrial electrodes. This list is not exhaustive and other sensing vector combinations may be developed to implement cardiac response classification in accordance with embodiments of the invention. For example, other vectors may include a coronary sinus electrode, an indifferent electrode, a leadless ECG electrode, cardiac epicardial electrodes, subcutaneous electrodes, and/or other electrodes.
It is understood that the components and functionality depicted in the figures and described herein can be implemented in hardware, software, or a combination of hardware and software. It is further understood that the components and functionality depicted as separate or discrete blocks/elements in the figures in general can be implemented in combination with other components and functionality, and that the depiction of such components and functionality in individual or integral form is for purposes of clarity of explanation, and not of limitation.
Various modifications and additions can be made to the preferred embodiments discussed hereinabove without departing from the scope of the present invention. Accordingly, the scope of the present invention should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.
Claims
1. A method of operating a cardiac device, comprising:
- delivering a pacing pulse to a heart chamber during a cardiac cycle;
- sensing a cardiac pacing response signal of the heart chamber during the cardiac cycle and following the pacing pulse in one or both of a first classification interval and a second classification interval, each of the first and second classification intervals associated with one or more timing parameters including at least a start time;
- adapting at least one timing parameter of one or more of the first classification interval, the second classification interval, and one or more blanking periods based on timing of at least one signal feature of the pacing response signal and a temporal relationship between the first classification interval and the second classification interval;
- applying the first and second classification intervals having the adapted timing parameters to a subsequent pacing response signal sensed following a subsequent pacing pulse delivered to the heart chamber;
- determining if the signal feature of the subsequent pacing response signal falls within the first or second classification intervals that have the adapted timing parameters;
- classifying a pacing response of the heart chamber to the subsequent cardiac pacing pulse based on a determination that the signal feature falls within the first or second classification intervals having the adapted timing parameters; and
- delivering cardiac therapy based on classification of the pacing response.
2. The method of claim 1, wherein the signal feature comprises a positive or negative peak.
3. The method of claim 1, wherein adapting the timing parameters based on the temporal relationship of the first and second classification intervals comprises adapting a start time of the second classification interval based on an end time of the first classification interval.
4. The method of claim 1, wherein adapting the timing parameter comprises adapting a timing parameter of a blanking period based on a temporal relationship between the blanking period and one or both of the first classification interval and the second classification interval.
5. The method of claim 1, wherein adapting the timing parameter comprises adapting timing parameters of three classification intervals, the first classification interval used to detect possible capture or fusion, the second classification interval used to confirm fusion, and a third classification interval used to confirm capture.
6. The method of claim 1, wherein adapting the timing parameter comprises at least one of:
- shortening one or more of the blanking periods and lengthening one or more of the first and second classification intervals; and
- lengthening one or more of the blanking periods and shortening one or more of the first and second classification intervals.
7. The method of claim 1, further comprising:
- comparing an amount of change in the timing of the signal feature compared to an initial timing of the signal feature to a threshold; and
- determining whether to adapt one or more of the first classification interval, the second classification interval, and the one or more blanking periods based on the comparison of the amount of change.
8. The method of claim 1, further comprising:
- comparing an amount of change in the timing of the signal feature compared to an initial timing of the signal feature to a threshold; and
- determining whether to re-initialize timing parameters of the first classification interval, the second classification interval, and the one or more blanking periods, wherein re-initializing the timing parameters involves acquiring a multi-sample electrogram of a pacing response signal.
9. A cardiac device, comprising:
- pacing circuitry configured to deliver a pacing pulse to a heart chamber during a cardiac cycle;
- sensing circuitry configured to sense a cardiac pacing response signal of the heart chamber during the cardiac cycle and following the pacing pulse in one or both of a first classification interval and a second classification interval, each of the first and second classification intervals associated with one or more timing parameters including at least a start time;
- control circuitry configured to adapt at least one timing parameter of one or more of the first classification interval, the second classification interval, and one or more blanking periods based on timing of at least one signal feature of the pacing response signal and a temporal relationship between the first classification interval and the second classification interval; apply the first and second classification intervals having the adapted timing parameters to a subsequent pacing response signal sensed following a subsequent pacing pulse delivered to the heart chamber; determine if the signal feature of the subsequent pacing response signal falls within the first or second classification intervals that have the adapted timing parameters; classify a pacing response of the heart chamber to the subsequent cardiac pacing pulse based on a determination that the signal feature falls within the first or second classification intervals having the adapted timing parameters; and deliver cardiac therapy based on classification of the pacing response.
10. The device of claim 9, wherein the control circuitry is further configured to adapt the timing parameters based on the temporal relationship of the first and second classification intervals comprises adapting a start time of the second classification interval based on an end time of the first classification interval.
11. The device of claim 9, wherein the control circuitry is further configured to adapt a timing parameter of a blanking period based on a temporal relationship between the blanking period and one or both of the first classification interval and the second classification interval.
12. The device of claim 9, wherein the control circuitry is further configured to adapt timing parameters of three classification intervals, the first classification interval used to detect possible capture or fusion, the second classification interval used to confirm fusion, and a third classification interval used to confirm capture.
13. The device of claim 9, wherein the control circuitry is further configured to:
- compare an amount of change in the timing of the signal feature compared to an initial timing of the signal feature to a threshold; and
- determine whether to adapt one or both of the first and second classification intervals based on the comparison of the amount of change.
14. A method of operating a cardiac device, comprising:
- delivering at least one pacing pulse to a heart chamber;
- sensing a pacing response signal of the heart chamber following the pacing pulse;
- detecting a temporal event of the pacing response signal, the temporal event comprising a point in time that falls between a first feature and a second feature of the pacing response signal; and
- initializing timing parameters of one or more of pacing response classification intervals and one or more blanking periods based on the detected temporal event so that the first feature falls within a first classification interval and the second feature falls within a second classification interval.
15. The method of claim 14, wherein sensing the pacing response signal further comprises acquiring a multi-sample electrogram of the pacing response signal.
16. The method of claim 14, wherein detecting the temporal event comprises detecting a zero crossing point of the pacing response signal.
17. The method of claim 14, wherein detecting the temporal event comprises detecting an inflection point of the pacing response signal.
18. The method of claim 14, wherein detecting the temporal event comprises detecting a midpoint between a time of occurrence of the first feature and a time of occurrence of the second feature.
19. The method of claim 14, wherein:
- detecting the temporal event comprises detecting a zero crossing point, an inflection point or a mid-point of the cardiac signal; and
- initializing the timing parameters of the one or more classification intervals and the one or more blanking periods comprises setting a start time of a blanking period and an end time of a classification interval to coincide with the zero crossing point, inflection point or mid-point.
20. The method of claim 14, wherein initializing the timing parameters of the one or more blanking periods comprises initializing to allow sensing of the first or second feature.
21. The method of claim 14, wherein initializing the timing parameters of the one or more blanking periods comprises initializing to prevent sensing of signal features other than the first or the second features.
22. A cardiac device, comprising:
- pacing circuitry configured to deliver at least one pacing pulse to a heart chamber;
- sensing circuitry configured to sense a pacing response signal of the heart chamber following the pacing pulse and detect a temporal event of the pacing response signal, the temporal event comprising a point in time that falls between a first feature and a second feature of the pacing response signal; and
- control circuitry configured to initialize timing parameters of one or more of pacing response classification intervals and one or more blanking periods based on the detected temporal event so that the first feature falls within a first classification interval and the second feature falls within a second classification interval.
23. The device of claim 22, wherein the sensing circuitry is further configured to acquire a multi-sample electrogram of the pacing response signal.
24. The device of claim 22, wherein:
- the sensing circuitry is further configured to detect a zero crossing point, an inflection point, or a mid-point of the cardiac signal; and
- the control circuitry is further configured to initialize the timing parameters of the one or more classification intervals and the one or more blanking periods and to set a start time of a blanking period and an end time of a classification interval to coincide with the zero crossing point, inflection point, or mid-point.
25. A method, comprising:
- delivering a pacing pulse to a left ventricle of a heart;
- sensing a cardiac pacing response signal of the left ventricle;
- detecting a first peak in a first capture detection interval and detecting a second peak in one of a fusion detection interval and a second capture detection interval that follows the fusion detection interval; and
- discriminating between capture and fusion based on the first and second peaks.
26. The method of claim 25, wherein detecting the first peak in the first capture detection interval comprises detecting the first peak in a capture detection region within the first capture detection interval, the capture detection region having upper and lower timing boundaries and upper and lower amplitude boundaries.
27. The method of claim 25, wherein discriminating between capture and fusion comprises classifying the pacing response as potential capture if the first peak falls within the capture detection region and confirming capture if the second peak falls within the second capture detection interval.
28. The method of claim 25, wherein discriminating between capture and fusion comprises classifying the pacing response as fusion if the second peak falls within the fusion detection interval.
29. A device, comprising:
- pacing circuitry configured to deliver a pacing pulse to a left ventricle of a heart;
- sensing circuitry configured to sense a cardiac pacing response signal of the left ventricle and detect a first peak in a first capture detection interval and detecting a second peak in one of a fusion detection interval and a second capture detection interval that follows the fusion detection interval; and
- control circuitry configured to discriminate between capture and fusion based on the first and second peaks.
30. The device of claim 29, wherein the sensing circuitry is configured to detect the first peak in a capture detection region within the first capture detection interval, the capture detection region having upper and lower timing boundaries and upper and lower amplitude boundaries.
Type: Application
Filed: Nov 29, 2011
Publication Date: Nov 29, 2012
Inventors: Yanting Dong (Lexington, KY), Shibaji Shome (Arden Hills, MN), Aaron McCabe (Minneapolis, MN), Amy J. Brisben (St. Paul, MN), Clayton Foster (Andover, MN), David W. Yost (Brooklyn Park, MN), Kenneth N. Hayes (Blaine, MN)
Application Number: 13/306,611
International Classification: A61N 1/37 (20060101); A61N 1/365 (20060101);